This invention relates to an index apparatus used in a floppy-disk apparatus or the like and, in particular, to an apparatus for detecting and adjusting an index.
A floppy disk has an index which indicates a physical position in the rotating direction of the disk. If the accuracy of this position is deteriorated to a certain extent, reading errors will result.
A conventional index apparatus for detecting such an index utilizes an outer peripheral section of the magnet of a frequency generator (hereinafter abbreviated as "FG") for detecting the speed of the motor. The outer peripheral section of this magnet is coated with a paint or the like that has a low light reflectance. A film or the like (which is, e.g., silver in color) having a high light reflectance is glued to a section of the coated surface. A reflection-type optical sensor is used to generate an index pulse by utilizing a difference in light reflectance due to the above structure.
A problem with the above conventional index apparatus is that the section exhibiting a low light reflectance is realized by painting, resulting in a variation in light reflectance caused by any unevenness in the painting.
Furthermore, since the section exhibiting a high light reflectance is realized by gluing a film to the coated surface, the apparatus is subject to dislocation in the gluing or to separation of the film from the coated surface. Moreover, since this gluing process cannot be automated, considerable man-hours are required for assembly, resulting in high production costs.
A conventional apparatus for index adjustment adjusts an index sensor for generating an index pulse through mechanical positional adjustment in such a way that an index burst signal recorded in media for adjustment (hereinafter referred to as "alignment media") is kept within an adjustment standard.
However, since the above conventional index apparatus is subjected to mechanical adjustment after it has been incorporated in the floppy-disk drive, the adjusting operation is rather complicated. It is thus necessary to provide an index-sensor guide section for adjustment.
Further, when performing fine adjustment for the mechanical adjustment, a correct adjustment cannot be effected because of the fixing screws and the like.